16. _______ medicine works in a human body is a question _______ not everyone can understand fully.
After describing the planned improvements, she went on _______ how much they would cost.
The film star walked to his car, ______ a crowd of journalists.
_______ on time, this medicine will be quite effective.
When I handed the report to John, he said that George was the person _______.
He is a man of few words, and seldom speaks until _______ to.